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Summary:

Acoustic pingers (Dukane Netmark 1000; frequency of 10-12 kHz and emit 300 ms tone every 4 sec with a source level range of 120-146 dB) were assessed to determine the effectiveness for reducing bycatch of dolphins and porpoises (common dolphins, dusky dolphins, bottlenose dolphins, Burmeister's porpoise, and pilot whales) by Peruvian small-scale driftnet fleets. Pingers were tested between April 2009 and August 2011. Twenty-two percent of the control nets captured small cetaceans and 16% of experimental nets captured small cetaceans. This was a 37% reduction in bycatch rates, suggesting that pingers may be effective in reducing bycatch of small cetaceans in this fishery. Catch rates of the fishery's target shark and ray species was not changed. 

Summary:

Two porpoises were subjected to 3 different underwater sounds (standard Dukane alarm, random Dukane alarm, and a "bird alarm") in a enclosed floating pen. Their behavior during a 15 min test period was compared to behavior during a baseline 15 min period before the test and a recovery period after the test. All alarms resulted in increases in both the distance of the animals' surfacings from the alarms and their respiration rates. The standard Dukane alarm and the bird alarm were more effective than the random alarm in inducing animals to swim away from the source. 

Summary:

Two captive harbor porpoises were exposed to three sound types (frequency from 100 kHz to 140 kHz, 200 ms long, and presented once per 4 s). Each session consisted of a 10 min period persound, a 5 min period of sound, and a 10 min period after the sound. Behavior was recorded on video and with dataloggers. Animals reacted most to the intial presentations of sound, but the reactinos diminished rapidly in repeated sessions. 

Summary:

A field test was conducted to test whether harbor porpoises habitutate to pingers over time. Echolocation and movements were monitored around a mooring equipped with a pinger (Dukane Netmark 1000) for 3 months. Initial displacement was 208 m from the pinger, but it diminished by 50% within 4 days. Echolocation rate and occurrence were significantly reduced near the pinger. 

Summary:

This study qualitatively describes accidents between cetaceans and fishing boats on the Brazilian coast and the Central Amazon region through the perception of artisanal fishers. From 2005 to 2010, 215 interviews were conducted. Fishers identified encounters with five species: Inia geoffrensis, Sotalia guianensis, Tursiops truncatus, Eubalaena australis, and Megaptera novaeangliae. They said accidents occurred due to animal curiosity, high speed swimming, and calve protection. The authors propose co-management with local members, researchers, and the government to encourage feelings of collective ownership within communities aiming to minimize the number of collisions. 

Summary:

Potential risk of fisheries to cetaceans was assessed using a screening procedure based on a Productivity Susceptibility Analysis (PSA) using gears found in Ireland. Gillnets targeting demersal species was assessed as the fishery posing the greatest risk to cetaceans. Pelagic trawls targeting small pelagic species was found to pose a moderate risk to cetaceans. Specific gear-species interactions were also identified, such as humpback whales (Megaptera novaeangliae) and pots/traps.  

Summary:

Logbook and observer data were used to assess common bottlenose dolphin (Tursiops truncatus) bycatch patterns from 2003 to 2009 in the Pilbara trawl fishery. Dolphins were caught in all fishery areas, across all depths, and throughout the year. The bycatch rate from observers was 12.6 dolphins/1,000 trawls, which was double the rate reported in logbooks. The most significant predictors of dolphin catch were: vessel, time of day, and the use of bycatch reduction devices (BRDs). BRDs reduced catch by 45%.

Summary:

Information on the use of Dolphin Wall Nets (DWN) by fisherman in Kerala, India was presented in this paper.  The DWN was designed by these fishermen to reduce dolphin attacks during fishing operations. Specifically humpbacked dolphins tend to congregate in fishing areas, surrounding the ring seine net and removing fish from the net.  This net design can be used by fishermen instead of crackers, which can cause harm to the dolphins. The authors provided fishermen from four stations in Kerala, India (Kasargode, Kozhikode, Ernakulum and Kollam) questionnaires to fill out. The questionnaires were designed to collect information on ring seine fishing operations, dolphin attacks and the structural details of the DWN when it was used.  The authors presented results on the structure of the DWN used by these fishermen but did not report any information regarding differences in bycatch rates between regular ring net operations and those using DWN.

Summary: Trials to assess the behavioural response of free-ranging bottlenose dolphins to continuous and responsive pingers were conducted. In boat based trials both types of pinger affected dolphin behaviour, while in static trials the detection of dolphin vocalisations was significantly lower in the presence of active continuous pingers.

Summary:

This article reviewed bycatch mitigation methods that rely on sensory ecology to reduce interactions with sea birds, sea turtles, pinnipeds and blue-water fish. Panels containing patterns of low spatial frequency and high internal contrast can be used for all of these species. These panels are not likely to reduce catches of target species and are easy and inexpensive to apply. The authors suggest that sound signals on gillnets are not recommended for most bycatch species, excpet for cetaceans. Cetaceans require both visual cues and warning through echolocation.